Metabolites are synthesized and regulated by various metabolic processes and pathways. Each metabolite and its metabolic pathways are inevitably involved in certain biological processes of a system, e.g., human and could play an important role in a system's function and regulation. Therefore, it is useful to understand how metabolites, e.g., lipid metabolites are regulated by their biosynthesis pathways. There is a great need in the field to develop various ways to assess metabolic processes or pathways, e.g., measure contributions of pathways to metabolite productions.